King Lear is a great work of a great playwright(not needed to mention his name). Characters are the mainspsing of his plays. In king Lear also we see Lear to be the centre of everything. It is in fact the story of Lear's achieving self-knowledge. The theme of the play for no doubt is purgation. The storm is the most significant thing to achieve the theme.
In the very beginning of the play we find lear as a man of wrong justice. He does a great wrong by disinheriting his own daughter Cordelia because of her inability to flatter him. Room after dividing the kingdom no the basis of oily words lear comes to understand that what he has done is a great wrong.
'O, Most small fault' was his expression. This understanding is a significant part of his regeneration. Next we see him showing sympathy for a fellow sufferer in regan's court in his process to be a man.
But the climax of his regeneration is held in the storm. In a stormy night we see Lear left the court for outside where a violent storm and rain blows. Whe Kent in disguise invites him to the hovel he doesn't forget the fool. Here he treats him as his own son 'Come on my boy'. Here he treats the fool not as a subject but as a fellow sufferer. Then the sight of Edgar in disguise of poor Tom enables him to realise the distress of humanity in the Earth in general. He fell into deep sleep and when he gets up he becomes a totally changed man.
Thus it can be said easily that the theme of the play King Lear is purgatory. And it is nothing but the storm which enables the protagonist to achieve self-knowledge through lots of suffering and pain..